Lots of terms are used to refer to this tool, some say the Avometer because it refers to its use from the units used in Ampere, Volt and Ohm. Multimeter from the word Multi (many) and Meter (connoted as a measuring instrument). Multitester of the word Multi (many) and tester (tool to test).
Before we use it, it would be nice if we get to know the panels, terminals, and facilities that this electronic measuring instrument has.
MEASUREMENT LIMIT (BU) on the Multimeter as follows.
Measure Limit is the maximum value that can be measured by the multimeter
The top left is the DC Volt selector block. This is the selector block that we must choose when making DC voltage measurements. Keep in mind that this is a measurement limit (BU) that we must pay attention to when making measurements. If the estimated value of the voltage to be measured is known, the Measure Limit to be chosen must be above the estimated value. For example, if we are going to measure the voltage in a circuit that has a value stated on the PCB of 9 volts DC then we may use a limit of 10 volts DC.
The upper left is the AC Volt selector block. This is the selector block that we should choose when making AC voltage measurements. Likewise, for the measurement of the AC voltage, the Measure Limit that must be chosen must be above the estimated value of the AC voltage. Example If you are going to measure the PLN grid voltage, as we all know the value of the PLN voltage is in the range of 220 volts AC, you must choose a limit of 250 volts AC.
Below right is written Ohm unit for measuring resistance, this is not too critical or risky if you choose the wrong selector. It will only affect the accuracy and the way we calculate the measured resistance value.
The bottom left says DC mA which is used to measure DC current. The maximum measured current is 250 milli Ampere DC. the use of measuring limits must be above the estimated current value in the circuit.
If the estimated value of the voltage is not known, use the largest measuring limit (can be 1000 VoltDC or 1000 VoltAC). Likewise for DC currents use the highest measurement limit scale. The most important thing in measuring DC currents and voltages is that the polarity of the plug (probe) is not reversed. The cap (-) is connected to the black plug and the (+) is connected to the red plug.
If in the measurement there is a measurement limit error or the polarity of the plug is reversed, we should quickly pull the plug from the measuring point we are doing. This is on an analog multimeter at risk of damaging our measuring instrument even though the multimeter has a safety fuse.
II. MAXIMUM SCALE
Maximum Scale (SM) is the highest value limit on the meter panel.
At the very top of the Maximum Scale is the scale that is read when measuring resistance. It should be remembered that the pointing of the needle at the far right of the deviation is the value of the smallest resistance. Being at the far left deviation for or needle (moving slightly) indicates the greatest resistance value. Because the value of the resistance scale (ohms) to the far left has the largest number, while the rightmost value is zero.
In the image below, it is clear for the Maximum Scale of measuring currents, AC or DC voltages.
In the picture above, there are three values that are generally used on analog multimeters, namely the maximum scale of 10, 50, and 250.
III. MEASURING RESISTANCE
Place the selector or measuring limit (BU) of the most suitable resistance. Select the limit of measuring resistance so that it is close to the center of the scale. For example: on the scale shown below with a resistance of around 50 k, choose the × 1 k. Range.
Connect the two ends of the probe (plug) together. If the needle cannot point to the scale at zero, turn the ADJ ohm until the needle shows zero (remember the 0 scale on the right!). if it cannot be set to zero then the battery inside the meter needs to be replaced.
3. How to calculate the measured resistance value:
R = BU x JP
R = measured resistance (ohms)
BU = Measure limit used
JP = Needle Designation on scale
so that in the example above we can calculate the measured resistance has a value:
BU = x 1K
JP = refers to the number 50 ohms
counted:
R = 1K x 50
R = 50K ohms
Work safety
In using a multimeter as a voltage meter we must pay attention to the manual book of each multimeter, which can be summarized as follows: Install the probe according to its position. The red probe is plugged into the (+) terminal, and the black probe is plugged into the com (-) terminal. There are some multimeters that have a probe included with the multimeter, so you don't need to bother installing. Voltage type. Before taking measurements, we must know what type of voltage we are measuring, whether AC (alternating current) or DC (direct current) voltages.
By knowing the type of voltage we can determine the placement of the selector on the AC section
or DC. If the voltage we are measuring is AC voltage point the selector at the AC section. If the voltage we are measuring is DC voltage then point the selector at the DC section. If we don't know the type of voltage, to be safe in the measurement, you should point the selector at the AC section (because DC voltage is actually part of the AC voltage).
IV. Measurement of DC currents and voltages with a multimeter
Choose a measuring range greater than the readable reading.
Connect the meter, making sure the connection is on the correct side. The Digital Meter will survive reverse connection, but the analog meter may become damaged.
If the reading exceeds the scale: release as soon as possible and choose a higher measuring range.
Multimeters are very easily damaged by careless treatment please pay attention to this:
Always remove the meter before moving the meter.
Always check the location of the steps before connecting the circuit.
Do not leave the meter in the current measurement (except when taking the measurement).
The range of the current meter has the greatest risk of damage because it is at a low resistance.
How to measure voltage:
Connect the black lead (negative -) to 0V, normally the negative terminal of the battery or power supply. red tip (positive +) point where you want to measure voltage.
Analog scale reading:
Pay attention to the placement of the meter switch select the appropriate scale. For some measurement ranges you will need to multiply or divide by 10 or 100 as shown in the reading below. For the AC voltage measurement range, use a red mark because the scale calibration is slightly shifting.
An example of a scale reading is shown at :
- DC 10V range: 4.4V (read directly scale 0-10)
- DC 50V range: 22V (read 0-50 scale directly)
- DC 25mA range: 11mA (read 0-250 and divide by 10)
- AC 10V range: 4.45V (use red scale, read 0-10)
Formula :
- VDC = DC voltage
- BU = Measure Limit
- SM = maximum scale used
- JP = Pointing Needle
How to calculate :
For example, the Measure Limit used is 10 VDC with a Maximum Scale of 10 VDC and the needle above points to 4 over 2 small columns, each small column is worth 0.2 because between numbers 4 and 5 (not written), it is divided into (5 small columns) So that JP = 4,4
VDC = (BU / SM) JP
= (10/10) 4.4
measured value = 4.4VDC
V. MEASURING AC VOLTAGE
Use dry footwear made of insulating material as minimal protection in the event of an electric shock. This needs to be done when measuring the AC voltage which is considered large. Before making a voltage measurement, we should be able to estimate how much voltage to measure, this is used as a reference for determining the Measurement Limit that must be used. The selection of the appropriate measuring limit should be higher than the measured voltage.
For example: for PLN voltage measurement, it is known that the type of voltage is AC and the voltage is 220 VAC, so the measurement limit that must be used is 250 or 1000. If you do not know the voltage value to be measured, select the highest measurement limit.
The red probe plugs into the (+) terminal, and the black probe plugs into the (-) terminal on the multimeter.
Specifies the Measure Limit for measurements. Because the PLN voltage in theory is 220VAC, we point the selector at the VAC section with a Measure Limit of 250 or 1000 (remember the Measure Limit is chosen to be greater than the voltage to be measured). For our discussion this time we will use the Measure Limit of 250.
In AC voltage measurement, the probe can be placed back and forth.
Connect the two ends of the multimeter probe to each of the two poles of the PLN voltage line, for example a socket.
Pay attention when taking measurements, do not let the red and black probe leads touch each other, as this will cause a short circuit.
From these measurements, the needle designation is obtained as follows.
How to determine the reading of the measured results, the formula used is no different when we calculate the DC voltage measurement results.
- BU = Measure Limit
- SM = maximum scale used
- JP = Pointing Needle
- VAC = Rated voltage
In our measurement above the Measurement Limit used is 250 Vc and the Maximum Scale used is 250, as well as the needle designation at 200 over 4 small columns where each column is worth 5 so that if we point to 220. from this data it is known BU = 250, BC = 250 and JP = 220.
so we just need to enter the formula above as follows:
Vac = (250/250) 220
Vac = 220
For other measurement applications, we do the same thing, for example the output of a step-down transformer which is an AC voltage. To measure it, first determine the measurement limit by referring to the estimated value printed on the transformer. Then touch the tip of the multimeter probe to each of the transformer output terminals to be measured. Of course, the primary transformer terminal must be connected to the PLN voltage.
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